Making particles pile up on the floor
First of all, after seeing your scene, increase your particles lifetime so they can actually reach the floor. 

Then you need to create an actual collision object, because physical objects do only interact with special defined collision objects.  



At deafult settings, the particles are bouncing very heavy after touching the collision object and if you want to change this bounciness you have to go to your collision object and change the stickiness.

And If you want to prevent them from gliding on the floor, increase the friction.